This invention relates to a phosphor having a special effect when applied to a deluxe fluorescent lamp and a phosphor screen of cathode ray tube, and more particularly to an alkaline-earth metal silicate phosphor activated by trivalent terbium (Tb.sup.3+).
In the latest deluxe fluorescent lamps, a mixture of several kinds of phosphors in an appropriate proportion is used to obtain a proper spectral power distribution in a visible region and also obtain a high color rendering index. As a green-emitting phosphor for such lamps, zinc silicate activated by divalent manganese has been usually used so far. The emission peak wavelength (.lambda.p) of the zinc silicate phosphor is approximately equal to 525 nm. For example, when said zinc silicate phosphor is used as a green-component phosphor for the deluxe cool white lamp based on a blend of three phosphors, i.e. blue, red and green-emitting phosphors, the emission peak wavelength (.lambda.p) is disadvantageously small. For a cool white lamp with color temperatures of 4100K and CIE chromaticity coordinate of x = 0.380 and y = 0.390, calculations show that a green-component phosphor peaking at 535 .+-. 8 nm (.lambda.p) is required for general color rendering indices R.sub.a greater than or equal to 85.